Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
  • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
  • F01N3/033—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices
  • F01N3/035—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters in combination with other devices with catalytic reactors
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
  • B01J23/42—Platinum
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
  • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
  • B01D53/34—Chemical or biological purification of waste gases
  • B01D53/92—Chemical or biological purification of waste gases of engine exhaust gases
  • B01D53/94—Chemical or biological purification of waste gases of engine exhaust gases by catalytic processes
  • B01D53/944—Simultaneously removing carbon monoxide, hydrocarbons or carbon making use of oxidation catalysts
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
  • B01J23/44—Palladium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/18—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the mordenite type
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/19—Catalysts containing parts with different compositions
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/024—Multiple impregnation or coating
  • B01J37/0244—Coatings comprising several layers
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/024—Multiple impregnation or coating
  • B01J37/0246—Coatings comprising a zeolite
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/024—Multiple impregnation or coating
  • B01J37/0248—Coatings comprising impregnated particles
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
  • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
  • F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/02—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust
  • F01N3/021—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters
  • F01N3/022—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous
  • F01N3/0222—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for cooling, or for removing solid constituents of, exhaust by means of filters characterised by specially adapted filtering structure, e.g. honeycomb, mesh or fibrous the structure being monolithic, e.g. honeycombs
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
  • F01N3/0821—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents combined with particulate filter
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
  • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
  • F01N3/0807—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents
  • F01N3/0828—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by using absorbents or adsorbents characterised by the absorbed or adsorbed substances
  • F01N3/0835—Hydrocarbons
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/10—Noble metals or compounds thereof
  • B01D2255/102—Platinum group metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/206—Rare earth metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/207—Transition metals
  • B01D2255/20738—Iron
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/20—Metals or compounds thereof
  • B01D2255/207—Transition metals
  • B01D2255/20761—Copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/50—Zeolites
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/90—Physical characteristics of catalysts
  • B01D2255/912—HC-storage component incorporated in the catalyst
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D2255/00—Catalysts
  • B01D2255/90—Physical characteristics of catalysts
  • B01D2255/915—Catalyst supported on particulate filters
  • B01D2255/9155—Wall flow filters
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/08—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y
  • B01J29/10—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the faujasite type, e.g. type X or Y containing iron group metals, noble metals or copper
  • B01J29/12—Noble metals
  • B01J29/126—Y-type faujasite
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/70—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65
  • B01J29/72—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of types characterised by their specific structure not provided for in groups B01J29/08 - B01J29/65 containing iron group metals, noble metals or copper
  • B01J29/74—Noble metals
  • B01J29/7415—Zeolite Beta
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J29/00—Catalysts comprising molecular sieves
  • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
  • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
  • B01J29/80—Mixtures of different zeolites
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N2370/00—Selection of materials for exhaust purification
  • F01N2370/02—Selection of materials for exhaust purification used in catalytic reactors
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N2370/00—Selection of materials for exhaust purification
  • F01N2370/02—Selection of materials for exhaust purification used in catalytic reactors
  • F01N2370/04—Zeolitic material
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N2510/00—Surface coverings
  • F01N2510/06—Surface coverings for exhaust purification, e.g. catalytic reaction
  • F01N2510/063—Surface coverings for exhaust purification, e.g. catalytic reaction zeolites
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
  • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES
  • F01N2510/00—Surface coverings
  • F01N2510/06—Surface coverings for exhaust purification, e.g. catalytic reaction
  • F01N2510/068—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings
  • F01N2510/0682—Surface coverings for exhaust purification, e.g. catalytic reaction characterised by the distribution of the catalytic coatings having a discontinuous, uneven or partially overlapping coating of catalytic material, e.g. higher amount of material upstream than downstream or vice versa
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
  • Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
  • Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S502/00—Catalyst, solid sorbent, or support therefor: product or process of making
  • Y10S502/514—Process applicable either to preparing or to regenerating or to rehabilitating catalyst or sorbent

Definitions

• the invention relates to a catalytically coated diesel particulate filter for cleaning the exhaust gases of diesel engines, a method for coating the filter and its use.
• Particulate filters are able to filter out particulate exhaust gas constituents, especially soot particles, from the exhaust gas of internal combustion engines and thus prevent their emission into the atmosphere.
• surface and depth filters can be used for this purpose.
• Surface filters are usually made of ceramic materials, e.g. Silicon carbide, corderite, aluminum titanate or mullite. Filtration levels of more than 95% are achieved with these filters.
• open structures for the separation of soot particles. These open structures are primarily ceramic foams or filters made of metallic wire mesh. The filtration efficiency of these open filter systems is significantly lower than the typical surface filters ( ⁇ 70%).
• the real challenge in operating a particulate filter in the exhaust gas of an internal combustion engine is not the filtration of the soot particles, but the periodic regeneration of the filters used. Since the measures necessary for igniting and burning the soot with oxygen to temperatures exceeding 550 0 C in modern passenger car diesel engines can only be achieved in full load usually, additional measures for the oxidation of the filtered soot particles are imperative in order to prevent blocking of the filter. Generally speaking, a distinction is made here between passive and active heating measures. In the active measures to increase the temperature of the particulate filter, for example, an electric heater (eg glow pins or microwave heaters) or a fuel-operated burner is used. Such active measures always go hand in hand with increased fuel requirements.
• an electric heater eg glow pins or microwave heaters
• passive measures In passive systems, the use of catalysts reduces the ignition temperature required to burn soot particles. This can be achieved by two different concepts.
• One concept is the use of organometallic fuel additives, such as cerium and iron compounds, which are burned with the fuel and store as a homogeneous catalyst finely distributed in the form of metal clusters in the soot layer.
• An alternative to the additive-based systems is the coating of the particle filter with a catalytically active material.
• the filters were usually arranged after one or two upstream oxidation catalysts in the underbody of the motor vehicle.
• the filters are installed as close as possible behind the engine. Because of the limited space and to reduce the cost of the oxidation catalyst is applied partially or completely on the filter in these cases.
• Such a filter arranged close to the engine must have a correspondingly high oxidation potential in order to comply with the legally prescribed limit values for carbon monoxide (CO) and hydrocarbons (HC) over the required mileage feature.
• the catalytically active coating for the close-coupled use of such a filter must have a high thermal stability.
• WO 02/26379 A1 describes inter alia a soot filter which contains two catalyst layers lying one above the other.
• the first layer is located on the inlet channels of the filter and contains components for the oxidation of carbon monoxide and hydrocarbons. These components consist of support materials with platinum group metals deposited thereon, wherein the support materials are selected from the group consisting of alumina, silica, titania, zirconia and zeolite and the platinum group metals are selected from platinum, palladium and rhodium.
• the second layer is applied to the first layer and contains components for reducing the ignition temperature of carbon black, in particular at least one oxygen-storing compound and at least one platinum group metal.
• the object of the invention is to provide a catalytically coated diesel particulate filter with an improved conversion for carbon monoxide and hydrocarbons, which also has a high aging stability even with frequent repeated regenerations of the filter.
• the particulate filter has an inlet side and an outlet side for the exhaust gases and an axial length.
• the filter is coated over its entire length with a first catalyst containing as catalyst active components platinum group metals on support materials.
• the filter is characterized in that the support materials for the platinum group metals are selected from the group consisting of alumina, silica, titania, zirconia, ceria and mixtures or mixed oxides thereof and that the first catalyst additionally contains at least one zeolite for storage of hydrocarbons.
• the particle filter is coated from the inlet side to a fraction of the length with a second catalyst containing no zeolite.
• the zeolites used for the first catalyst preferably have a modulus (molar ratio of SiO 2 to Al 2 O 3) greater than 10 in order to be sufficiently stable to the acid components of the exhaust gas and the maximum exhaust gas temperatures.
• Suitable zeolites are, for example, mordenite, silicalite, Y zeolite, ZSM-5 zeolite and beta zeolite or mixtures thereof, wherein the zeolites have a silica to alumina molar ratio between 10 and 400.
• other materials such as activated carbon can be used.
• the zeolites store the hydrocarbons contained in the exhaust gas. This is important because at these low exhaust temperatures, oxidation of the hydrocarbons at the active noble metal centers of the catalyst is not possible. Such operating phases occur in modern passenger car diesel engines both during a cold start and during idle periods and in city traffic. At temperatures above about 200 0 C, however, outweighs the desorption of hydrocarbons. At these higher catalyst temperatures, however, the hydrocarbons released from the storage components at the active centers of the catalyst can be converted to carbon dioxide and water.
• the zeolites may additionally be catalytically activated with platinum group metals (platinum, palladium, rhodium, iridium) or with transition metals (for example iron, copper, cerium).
• platinum group metals platinum, palladium, rhodium, iridium
• transition metals for example iron, copper, cerium
• the zeolites may be impregnated with aqueous solutions of soluble precursor compounds. After impregnation, the zeolites are dried, calcined and optionally reduced.
• the noble metal loading on the zeolites is preferably between 0.1 and 10 wt .-%, based on the total weight of zeolites and platinum group metals.
• the zeolites in the ammonium or sodium form are doped by ion exchange with the transition metals.
• the ion exchange can be carried out either in solution or as so-called solid-state ion exchange.
• the loading of transition metals is preferably about 1 to 15 wt .-% based on the total weight.
• the first catalyst contains at least one or more platinum group metals, preferably a combination of platinum and palladium with a weight ratio of platinum to palladium from 1:10 to 20: 1, preferably from 1: 1 to 10: 1, in particular 2: 1.
• carrier materials for the platinum group metals are alumina, silica, titania, zirconia, ceria and mixtures or mixed oxides thereof.
• the support materials can be thermally stabilized by doping with rare earth oxides, alkaline earth oxides or silicon dioxide. For example, in aluminum oxide by doping with barium oxide, lanthanum oxide or silicon dioxide, the transformation temperature of ⁇ - to CC-alumina of about 950 to 1100 0 C increased.
• the concentration of the doping elements calculated as oxide and based on the total weight of the stabilized aluminum oxide is usually 1 to 40 wt .-%.
• cerium oxide as a carrier material
• cerium / zirconium mixed oxides since these generally have a higher Have temperature stability as the pure ceria.
• the stability of the cerium / zirconium mixed oxides can be further improved by doping with praseodymium oxide or neodymium oxide.
• cerium / zirconium mixed oxides also have advantageous oxygen storage properties, both in terms of maximum oxygen storage capacity and the kinetics of oxygen storage and release.
• the particle filter is coated from the inlet side on a fraction of its length with the second catalyst.
• This second catalyst may be identical or different with the first catalyst both with respect to the catalytically active noble metals and with respect to the support materials used.
• a catalyst having the same composition as the first catalyst is used for the additional coating.
• the second catalyst contains no zeolites.
• the length of the second catalyst may be 5 to 80% of the total length of the filter substrate, preferably 10 to 50%.
• the application of the second catalyst from the inlet side of the filter leads to a stepped concentration of the catalytically active components.
• In the front part of the filter are more catalytically active components.
• This is particularly advantageous with diesel particulate filters with integrated oxidation catalyst arranged close to the engine.
• NEDC New European Driving Cycle
• the introduction of the catalyst materials in the form of solid powder materials leads to catalytic activities and temperature resistances, which are clearly superior to the other two coating methods.
• the introduction in the form of solutions of precursors of the later support materials has distinct advantages with regard to the dynamic pressure behavior of coated particle filters and is therefore a suitable coating method, especially when using critical substrates (low porosity, small mean pore diameter).
• solid powder materials In the case of using solid powder materials, for example, they are suspended in water and ground to homogenize and adjust a defined particle size distribution. The grinding is carried out so that the maximum particle size in the suspension is less than 10 microns. This is usually the case when the dso diameter is less than 2 microns. Only this small particle size makes it possible to separate the catalyst almost exclusively in the pores of the substrate.
• the support materials used in the suspension are conventional already activated before introduction into the suspension with platinum group elements. However, it is also possible to add dissolved precursor compounds of the catalytically active platinum group metals only to the suspension of the support materials. Furthermore, even after the carrier materials have been applied to the filter substrate, a subsequent impregnation of the filter with soluble precursors of the platinum group metals can take place.
• Catalyst materials and zeolites have different hardnesses. Only by separate milling can a comparable particle size distribution be guaranteed for both materials. Therefore, two separate suspensions are initially used to coat the filters.
• the first suspension contains the carrier materials which are activated with noble metals (for example platinum, palladium).
• the second suspension contains the zeolites.
• the zeolites are preferably doped in a preceding process step by impregnation or ion exchange with noble metal. However, it is also possible to add precious metal to the zeolite suspension with the aid of suitable precursor compounds.
• both suspensions a mean particle diameter d.sub.so smaller than 2 .mu.m is then set separately by grinding; the dc > o value should be at a maximum of 5-6 ⁇ m.
• both suspensions are mixed and homogenized.
• Both first and second catalysts may contain zeolites. However, it has been found advantageous for diesel particulate filters arranged close to the engine if the zeolites are distributed uniformly over the entire length of the filter. In this case, only the first catalyst contains zeolites.
• the second catalyst then serves only to increase the concentration of the catalytically active noble metals in the front part of the particulate filter. In such an arrangement, in particular under transient conditions, such as in NEDC, for example, the strongly pronounced axial temperature profile in the filter can be optimally utilized in filter substrates made of silicon carbide.
• the distribution of the zeolites on the first and second catalyst affects the formation of the exhaust back pressure of the coated filters.
• the dynamic pressure is significantly higher than when the zeolites are applied with the first catalyst evenly over the entire length of the filter.
• the use of zeolites in the first and second catalyst has shown no significant difference in the dynamic pressure behavior with the same total zeolite loading compared to the exclusive arrangement of the zeolites in the first catalyst.
• the storage capacity for hydrocarbons increases with increasing amount of zeolites.
• the maximum usable amount of zeolites depends strongly on the porosity and the average pore diameter of the filter substrate used. Typical zeolite loadings range from 5 g / l (filter volume) for low porous substrates ( ⁇ 50%) to approx. 50 g / l for substrates with higher porosity (> 50%).
• the ratio of zeolites to the noble metal-doped carrier materials in the particulate filters according to the invention is preferably 0.1 to 10.
• the known filter substrates are suitable.
• so-called Wandflußfilter of silicon carbide, cordierite, aluminum titanate or mullite are used.
• the material of the filter should have an open-pore structure with a porosity between 40 and 80% and an average pore diameter between 9 and 30 microns.
• the substrates used were each silicon carbide filters with a cell density of 46.5 cm -1 (300 cpsi) and a channel wall thickness of 12 mils (0.3 mm) .
• the porosity of the filter material used was 60%.
• the mean pore diameter was 20 ⁇ m and the filter bodies had a length of 152.4 mm.
• Filter 1 was not loaded.
• Filter 2 was given a coating with an alumina suspension which after drying and calcination had a loading concentration of about 30 g / l.
• Filter 3 was coated with alumina and a zeolite mixture of a Y and a Beta zeolite (mixing ratio 1: 1). According to the invention, alumina and zeolites were ground separately until the mean particle size of alumina and of the zeolites was less than 2 ⁇ m.
• the loading of filter 3 was 30 g / l of alumina and 10 g / l of the zeolite mixture.
• a filter substrate was first coated homogeneously over the entire filter length with a Pt / Pd catalyst supported on a stabilized .gamma.-aluminum oxide.
• the coating suspension was ground until a mean particle diameter of less than 2 ⁇ m was reached.
• the catalyst material was deposited almost completely in the coating of the filter substrate in the coating.
• the Pt / Pd ratio of this first catalyst layer was 2: 1 and the noble metal loading was 2.12 g / l (60 g / ft).
• a second catalyst layer with a noble metal content of also 2.12 g / l (60 g / ft 3 ) and identical Pt / Pd ratio was applied over half the filter length.
• the resulting total precious metal loading of the comparative filter V was thus about 90 g / ft 3 , or 3.18 g / l.
• the second catalyst layer was also stored predominantly in the pores of the filter substrate.
• a second filter substrate was coated with the catalyst according to the invention.
• the filter was first uniformly coated over the entire filter length with a noble metal loading of 60 g / ft 3 .
• the coating according to the invention also contained a zeolite mixture of a Y and a beta zeolite (mixing ratio 1: 1) in addition to the stabilized .gamma.-aluminum oxide coated with Pt / Pd in a ratio of 2: 1. Both zeolites were doped with small amounts of Pt (0.5 wt.%) By impregnation prior to addition to the coating suspension.
• the ratio of ⁇ -aluminum oxide to zeolite mixture was about 1: 1.
• the inlet side of the 76.2 mm long filter was coated with an additional 2.12 g / l noble metal using the identical coating suspension.
• the total concentration of noble metals Pt and Pd on Filter Fl was thus 3.18 g / l (90 g / ft 3 ) at a Pt / Pd ratio of 2: 1.
• Example 1 Analogously to Example 1 (Filter Fl), two further filter substrates were coated with a noble metal loading of 3.18 g / l.
• the amount of zeolite of 20 g / l was applied exclusively in the first catalytic layer over the entire filter length.
• the zeolites were applied exclusively with the second catalyst layer.
• the zeolites used were, as in Example 1, a mixture of a Y zeolite and a beta zeolite (mixing ratio 1: 1). The two zeolites used were each doped with 0.5% by weight of Pt.
• the filter F2 and F3 show an improved emission behavior both with respect to the hydrocarbons emitted in the NEDC and also to the CO emissions.
• the use of HC memory components over the entire filter length proves advantageous.
• a breakdown of the zeolite amount on first and second catalyst shows no advantage compared to the exclusive use of zeolites in the first catalyst.
• the exclusive use of zeolites in the second catalyst is less favorable in terms of emissions of hydrocarbons and carbon monoxide in the NEDC.
• the HC emission increases by approx. 60% and the CO emissions increase by approx. 18%.
• the four filters were coated with different amounts of zeolite (from 10 to 40 g / l) with the same zeolite mixture of the 50th for both the first catalyst and the second catalyst % Y and 50% Beta zeolite as used with Filter Fl.
• the Pt concentration on the zeolites was 0.5% by weight.
• Table 2 shows the compositions of the four filters F4-F7 according to the invention.
• HC storage capacity of the filters according to the invention as a function of the zeolite content, storage tests were carried out on a 4-cylinder diesel engine Common rail injection system (2.2 1, 100 kW) performed. The storage tests were carried out at a constant engine operating point with a filter inlet temperature of approx. 110 ° C. HC emissions before and after the catalyst were recorded using an FID analyzer (AMA 2000, Pierburg). The storage experiments were each continued until the HC concentration after catalyst had reached a steady-state value for about 10 minutes. The amount of HC stored was determined from the HC concentrations before and after the catalyst:
• Table 2 Precious metal content and zeolite loading for the filters F4 to F7 and the amount of HC stored during the HC storage test on the engine test bench.
• the storage of hydrocarbons by the HC storage components reduces the adsorption of hydrocarbon species at the active oxidation centers of the catalyst. This also positively affects the conversion of carbon monoxide.

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